In this section, different approaches of grammars which generate two-dimensional languages are examined. Firstly, the Sironmoneys' models are introduced. They use several one-dimensional grammars to generate a string before it comes to generating a picture vertically. Furthermore, we will take a look at Rosenfeld grammars. His grammars are analogue to the one-dimensional ones, but replace subpictures instead of substrings. 